1. Technical Field
The invention is related to video signal processing for simple dedicated devices such as internet appliances or dedicated devices implemented as simple embedded operating systems.
2. Background Art
Internet appliances are embedded electronic systems at the edge of the internet. The market for these devices is just emerging and is expected to grow at he huge growth rate of internet technology. Internet appliances are typically characterized by the following characteristics that render them inexpensive: (1) low-speed internet connection and (2) limited hardware resources and therefore limited computational resources. It is felt that in the near future various consumer electronic devices that are commonly found in the home will be networked together with internet appliances in a home network and/or via the internet. Such internet appliances will include video devices such as cameras or displays.
One problem is that video signal processing and transmission requires a very large bandwidth. For example, the raw rate of High Definition Television (HDTV) is about one giga-bit per second. This bandwidth will not be available to home internet connections at least in the near future, and even if it were to become available soon, the transmission of raw or uncompressed video signals is not an efficient use of a network link. Thus, it is necessary to compress the video signal prior to transmission on a network or on the internet. Unfortunately, video compression requires significant computational resources well beyond the capability of an internet appliance. In order to produce high-quality images, most systems require very large computational resources and communication bandwidth. However, internet appliances have limited computational resources in part due to their inexpensive structure and because, in many cases, they are battery-powered and therefore do not have sufficient electrical power to support an intense computational effort. In typical video compression, the encoder (within the transmitter) is necessarily more complex than the decoder (within the receiver). This fact further exacerbates the problem of limited computational resources in an internet appliance in those cases in which the internet appliance is the originator or transmitter of video signals.
One approach to obtaining signal processing capability for application to voice data is described by Z. Tu and P Loizou, xe2x80x9cSpeech recognition over the Internet using Java,xe2x80x9d IEEE ICASSP 1999, Phoenix, Ariz. In this paper, it is proposed that a user can employ an internet browser such as Netscape Communicator to perform speech recognition by visiting a web site on a server that hosts applications capable of performing such a task. This browser-enabled architecture requires the voice to be recorded and sent to the speech-recognition server for processing. The results are then sent back to the client computer via the internet. However, when considered by the inventors herein as a possible application for signal processing by internet devices, several problems arose that would prevent such an application. First, the use of a browser in this proposal imposes computational requirements well beyond the capability of a typical internet appliance. Secondly, the browser must be pointed to the URL of the server with the web site hosting the desired signal processing application. Thirdly, the promptness and quality of service depends entirely on the maintenance of the remote web site and therefore cannot be guaranteed. Fourth, all of the raw data and processing results must be transmitted via the internet, which conflicts with the need to only transmit video data that has been compressed first to stay within a reasonable bandwidth.
Therefore, there is a need to process a video signal from or to an internet appliance so as to avoid using excessive bandwidth but without requiring more than very minor computational resources within the internet appliance.
A communication system embodying the invention has a communication channel with at least two ends, one end of the channel being connected to a transmission device with relatively limited computational capacity and an other end of the channel being connected to a computer having relatively large computational capacity. The transmission device includes a signal source node; a set of Mxe2x88x921 delay buffers connected in series and defining a set of M progressively delayed signal nodes, M being a positive integer, one end of the series of M delay buffers being connected to the signal source node; a set of M parallel downsampling operators connected to the M progressively delayed signal nodes; and, a parallel-to-serial converter having M parallel inputs and a single serial output, the M parallel inputs being connected to the outputs of the M parallel downsampling operators and the single serial output being coupled to the one end of the communication channel.
The computer has communication architecture including a serial-to-parallel converter having a single serial input and M parallel outputs, the single serial input being coupled to the other end of the communication channel; a set of M parallel filter coefficient multipliers having respective inputs and outputs and corresponding to the respective coefficients Hi(zxe2x88x921) of an anti-aliasing filter H(z)=xcexa3i=0Mxe2x88x921 zxe2x88x92iHi(zxe2x88x92M), the inputs of the multipliers being connected to respective ones of the M parallel outputs of the serial-to-parallel converter; and, a set of Mxe2x88x921 adders connected in series to define a set of M inputs and a single output, the outputs of the M multipliers being connected to respective ones of the set of M inputs defined by the series of adders, the single output of the series of adders being a received signal output.